1. Technical Field
This invention generally relates to concrete power trowels, and more particularly to transmissions and gearboxes for concrete power trowels.
2. Background
Concrete power trowels are used for finishing concrete surfaces as the concrete is curing and hardening. Power trowels come in two major types, xe2x80x9cwalk-behindxe2x80x9d power trowels where an operator walks-behind the power trowel, and xe2x80x9cridingxe2x80x9d power trowels where an operator rides on the power trowel.
A typical riding power trowel is a two-rotor device, with each rotor typically having multiple troweling blades extending out in radial fashion, and usually configured such that the tips of the blades of each rotor intermesh to provide for a continuous finishing of the concrete surface below the riding trowel.
While this application, for simplicity of the reader, discusses the present invention in reference to xe2x80x9cridingxe2x80x9d power trowels, the teachings of this application can likewise be applied to xe2x80x9cwalk-behindxe2x80x9d power trowels and intends to include such power trowels in the general usage of the term xe2x80x9cpower trowel.xe2x80x9d
A typical power trowel has a rigid frame housing at least one blade assembly, and an engine. The engine is usually a gasoline or diesel engine, and is used to provide the motive power for the blade assembly. Other potential xe2x80x9cenginesxe2x80x9d include, but are not limited to electric motors and hydraulic motors. For xe2x80x9cridingxe2x80x9d models, atop of the engine and the frame assembly is found an operator""s seat and the necessary control systems and levers for operation of the trowel. These machines are manufactured in a variety of sizes and weights, with the largest of these machines having not just two, but rather three, rotor and troweling blade assemblies.
While this application, in general, refers two rotor trowels, it is intended that the teachings of this application be equally applicable to any power trowels having one or more rotors.
Typically, in riding power trowels, the engine drives a horizontal drive line or shaft which extends between a first reduction gearbox and a second reduction gearbox. In the prior art, these reduction gearboxes utilize a worm gear on the horizontal drive line which cooperates with a mating gear on a rotor shaft to accomplish the reduction.
Examples of such riding power trowels can be found in U.S. patents to Holz, Sr. et al., U.S. Pat. Nos. 3,936,212, issued Feb. 3, 1976, and 4,046,484, issued Sep. 6, 1977. Additional examples of these prior art machines are disclosed in U.S. patents to Jaszkowiak, U.S. Pat. No. 5,816,740, issued Oct. 6, 1998, and Allen et al., U.S. Pat. Nos. 5,108,220 issued Apr. 28, 1992 and 5,238,323 issued Aug. 24, 1993.
A problem which exists in these prior art examples lies in the high amount of heat generated through use of such a gear arrangement. What is needed is a transmission/gear box for a power trowel which is mechanically more efficient, thereby reducing friction and heat within the gearbox and transmitting more power to the rotor assemblies. The present invention solves this problem.
One embodiment of the present invention is an improved self propelled power trowel for finishing a concrete surface. This improved power trowel has a rigid frame means which is adapted to be disposed over the concrete surface. The trowel has an engine assembly attached to the frame means for powering the power trowel. The engine assembly also has a clutch having an upper pulley which cooperates with a belt to drive a lower pulley located on or attached to a drive shaft, thereby rotating the drive shaft.
This embodiment of trowel has a left rotor assembly and a right rotor assembly for frictionally contacting the concrete surface and supporting the frame means there-above. These rotor assemblies are tiltably connected to the frame means and are operably connected to the engine assembly through use of a transmission system. The transmission system transmits the rotation of the engine (through use of the drive shaft) to the rotor assemblies. The transmission system further comprises a drive shaft, a first gearbox attached to the rigid frame means, and a second gearbox attached to the rigid frame means.
The drive shaft has a lower pulley for cooperating with the belt, a drive shaft first end cooperating with a first (or left) input shaft, and a drive shaft second end cooperating with a second (or right) input shaft. The first gearbox has a first housing having a first side opening and a first bottom opening. The first side opening receives therethrough the first input shaft. The first bottom opening receiving therethrough the first output shaft. The first input shaft connects to the drive shaft first end, and further to a first bevel gear for intermeshing cooperation with a second bevel gear located on a first intermediate shaft.
The first intermediate shaft has a first helical gear and the aforementioned second bevel gear. The first intermediate shaft is preferably oriented generally perpendicular to the first input shaft. The first helical gear being formed for intermeshing cooperation with a second helical gear located on the first output shaft. The first output shaft has the second helical gear, and is able to cooperate with the first rotor assembly to transfer the rotation of said first output shaft (ultimately driven by the drive shaft/engine) to the rotation of the first rotor assembly.
The right gearbox has a housing having a second side opening and a second bottom opening. The second side opening receives therethrough the right input shaft. The second bottom opening receives therethrough a right output shaft. The right input shaft connects to the drive shaft second end, and has a third bevel gear for intermeshing cooperation with a fourth bevel gear located on a right intermediate shaft.
The right intermediate shaft has a third helical gear and a fourth bevel gear. The right intermediate shaft is oriented generally perpendicular to the right input shaft. The third helical gear being formed for intermeshing cooperation with a fourth helical gear located on the right output shaft. The right output shaft has a fourth helical gear, and is for cooperating with the right rotor assembly to transfer the rotation of the right output shaft to the rotation of the right rotor assembly.
A second embodiment is a transmission system for a self propelled power trowel for finishing a concrete surface. This power trowel has: a rigid frame means adapted to be disposed over a concrete surface; an engine assembly for powering a power trowel attached to a frame means, wherein the engine means further comprises a clutch having an upper pulley which cooperates with a belt to drive a lower pulley located on a drive shaft; a left rotor assembly and a right rotor assembly for frictionally contacting the concrete surface and supporting the frame means thereabove, tiltably connected to the frame means and operably connected to the engine assembly through a transmission system for transmitting the rotation of the engine means to the rotor assemblies.
This embodiment""s transmission system has a drive shaft having a first end extending to at least one gearbox. The drive shaft further having at least one lower pulley able to cooperate with the belt of said engine assembly to be rotated and to rotate the drive shaft. The drive shaft first end attaches to an input shaft extending from the gearbox.
The transmission system further has a gearbox having a housing having a top, a bottom, at least one side wall, a side wall opening through the side wall, and a bottom opening through the bottom. The gearbox has a generally horizontal input shaft extending through the side wall opening. This input shaft having a first end and a second end. The input shaft second end being located outside of the housing and operably attaching to the drive shaft at the drive shaft""s first end. The input shaft first end further comprising a bevel gear.
The gearbox further has a generally vertical intermediate shaft rotatably mounted inside the housing, this intermediate shaft having a first end and a second end. The first end having a second bevel gear for intermeshing cooperation with the first bevel gear, and the second end having a first helical gear. The gearbox further has a generally vertical output shaft extending through the bottom opening, this output shaft having a first end and a second end. The second end being located outside of the housing and operably attaching to a rotor assembly. The first end being rotatably mounted within the housing. The output shaft having a second helical gear adjacent to the second end, this second helical gear for intermeshing cooperation with the first helical gear. It should be noted that the above-referenced helical gears could just as easily be spur gears, herring bone gears, or any other type of gear that transmits power in a similar manner. It should also be noted that the above-referenced bevel gears could be spiral-bevel gears, or any other type of gear that transmits power in a similar manner.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description wherein I have shown and described only the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated by carrying out my invention. As will be realized, the invention is capable of modification in various obvious respects all without departing from the invention. Accordingly, the drawings and description of the preferred embodiment are to be regarded as illustrative in nature, and not as restrictive.